Patent Application
20110210482
This invention relates to a resin molded body, in which a pipe portion and a flat plate portion are integrally injection molded, and a method for manufacturing the resin molded body, and more specifically relates to a resin molded body, which is operated as a heat-insulating plate or a radiator plate by passing a fluid through the pipe portion, and a method for manufacturing the resin molded body.
In the prior art floor heating system having a heat-insulating function, as shown in Patent Documents 1 and 2, for example, a complex of a pipe through which hot water is flowed, a hot water mat incorporated with the pipe or the like, and a floor material has been generally used.
Further, as a warm-water toilet seat, Patent Document 3 introduces an example in which an electrically-heated wire for keeping warmth is incorporated into a space between a cover plate and a base plate formed of a resin molded body to give a function of keeping warmth of the toilet seat.
Recently, in an automotive field, since a temperature in an engine room is increased due to performance improvement and environmental response, it has become an important issue to give a function of dissipating the heat of, for example, covers such as an engine head cover. In order to realize this issue, it has been proposed to increase the radiation efficiency by increasing a surface area from a design standpoint or by using a high thermal conducting material.
As a computer and a video apparatus become thinner and realize high performance, we are in urgent need of correspondence to internal heat generation of the apparatus. As a measure thereof, there has been proposed to utilize a radiation material in a housing of the apparatus, for example.
However, in the floor heating system disclosed in the Patent Documents 1 and 2, the pipe through which hot water passes and the hot water mat or the floor material are separate members. It takes a considerably high cost to unify and assemble those separate members. Since the pipe and the hot water mat or the floor material are not assembled so as to be completely fixed firmly to each other, there is a problem that the heat conducting efficiency is low.
The warm-water toilet seat disclosed in the Patent Document 3 is obtained by a combination of two resin molded bodies including a toilet seat cover plate and a base plate and a sheet heating element, and the assembly cost is required. It is inevitable that there is a gap between the heating element and the cover plate, so that the thermal efficiency is low.
It is not enough for an engine cover of a vehicle, housings of home appliances and OA equipment, and so forth, to give the radiation function from a material standpoint or a design standpoint as described above, and this remains an issue.
Accordingly, an object of this invention is to provide a resin molded body, which can give a heat-insulating or radiation function of providing extremely good heat transfer, has high reliability, and is manufactured with a simple process at low cost, and a method for manufacturing the resin molded body.
Namely, the resin molded body of this invention is characterized by being formed by integral injection molding of a pipe portion, which has at least a curved portion and flows a fluid therethrough, and a flat plate portion.
A method of manufacturing a resin molded body, according to the invention is characterized by including injecting a molten resin into a pipe cavity of a mold, the pipe cavity having on its end a pressure port provided with a floating core and on its other end an outlet, pressure-injecting a pressurized fluid through the pressure port after the injection of the molten resin, and moving the floating core toward the outlet, and, at the same time, extruding the molten resin from the outlet.
In the resin molded body of this invention, a fluid is passed through a pipe portion of the resin molded body, whereby the resin molded body is operated as a heat-insulating plate or a radiator plate. Since the pipe portion and a flat plate portion are integrally injection molded in the resin molded body, the resin molded body provides extremely good heat transfer, is free from leakage of the fluid, and requires no assembly cost.
Hereinafter, this invention will be described in detail using drawings.
In the resin molded body shown in
In order to allow a fluid such as a heating medium and a cooling medium to pass through the pipe portion 1, the pipe portion 1 preferably has a circular shape in the cross section of the hollow, and when an average inner diameter of the pipe is Φ, and maximum diameter−minimum diameter=R, the variation of the inner diameter R/Φ×100(%) is preferably not more than 20%. Namely, in order to flow the fluid smoothly, it is preferable that the cross section of the hollow of the pipe portion 1 has a circular shape, and the variation is small. The pipe portion 1 is subjected to an internal pressure for flowing the fluid, so that it is preferable that the thickness of the pipe portion 1 is even as much as possible at the request of design.
Since a resin molded product shown in
Although the resin used in this invention includes any type of thermoplastic resin and thermosetting resin capable of injection molding of a hollow body, the thermoplastic resin is preferably used in terms of hollow moldability in the injection molding. The thermoplastic resin includes various resins such as polystyrene, a polystyrene-based resin such as AS and ABS, a polyolefin-based resin such as polypropylene and polyethylene, a polyamide-based resin such as nylon 66 and nylon 6, a polyester-based resin such as PET and PBT, POM, polycarbonate, PPS, modified PPE, a PMMA resin, and a polyvinyl chloride resin. Further, there may be used those thermoplastic resins containing a reinforcing material, such as glass fiber, talc, calcium carbonate, and kaolin, or an inorganic filler. As the thermosetting resin, unsaturated polyester resin and phenol resin may be used, for example, if they are injection moldable thermosetting resins known as BCM. Moreover, recently, high thermal conductive resin or the like is available and is an example of a preferred resin of this invention.
In the resin molded body of this invention, a heating and heat-insulating medium such as hot water is passed as a fluid through the pipe portion 1, whereby the flat plate portion 4 can be evenly and efficiently heated and heat-insulated and is operated as a heat-insulating plate. Thus, the resin molded body can be suitably used in, for example, a resin molded body for household equipment having a heating and heat-insulating function, such as a wall and a floor heating and a heat-insulation toilet seat.
Meanwhile, a cooling medium such as cooling water and an antifreeze liquid is passed as a fluid through the pipe portion 1, whereby the flat plate portion 4 can be evenly and efficiently cooled and is operated as a radiator plate. Thus, the resin molded body of this invention can be suitably used in, for example, housings of various home appliances and OA equipment with the task of internal heat generation and an engine cover of a vehicle.
Since the resin molded body of this invention is obtained by integrally injection molding the pipe portion 1 and the flat plate portion 4, the resin molded body provides extremely good heat transfer, that is, has high heat efficiency or radiation efficiency. Since the resin molded body is obtained by integrally injection molding, no assembly cost is required, so that it is advantageous in terms of cost, and, at the same time, leakage of the fluid does not occur. Further, the pipe portion 1 can be molded without using a joint and welding means. The pipe portion 1 can be disposed two-dimensionally or three-dimensionally, so that the degree of freedom of design is high.
The resin molded body of this invention may be used alone; however, when the resin molded body of this invention is one unit, a plurality of pipes are connected by joints or the like, whereby each area of floor heatings of large to small sizes is covered, for example, so that the degree of freedom of design can be increased, and maintenance can be facilitated.
Next, a method of manufacturing a resin molded body of this invention will be described.
The method of manufacturing a resin molded body of this invention includes a gas assist injection molding method (for example, Japanese Examined Patent Publication No. 57-14968), water-assist injection molding (for example, plastic age (September 2007, page 106)), and a method using a floating core (for example, Japanese Examined Patent Publication No. 7-20646). In order to maintain uniformity of the inner diameter of a pipe over the entire area of the pipe, the injection molding method using a floating core is preferably used. More preferred is an injection molding method including a process of injecting a molten resin into a pipe cavity of a mold, the pipe cavity having on its one end a pressure port provided with a floating core and on its other end an outlet, pressure-injecting a pressurized fluid through the pressure port after the injection of the molten resin, and moving the floating core toward the outlet, and, at the same time, extruding the molten resin from the outlet.
Hereinafter, a method for manufacturing a resin molded body of
As shown in
An end 7 of the pipe portion cavity 1′ is provided with a floating core 5 and a pressure port 6. The floating core 5 has a diameter corresponding to the inner diameter of the pipe portion 1. A pressurized fluid for pressing and moving the floating core 5 toward the other end 8 of the pipe portion cavity 1′ is pressure-injected through the pressure port 6.
The floating core 5 is provided in the pipe portion cavity 1′ so that its back faces the pressure port 6, whereby the floating core 5 can be pressed by the pressurized fluid pressure-injected through the pressure port 6. The floating core 5 can be formed of a metal, such as copper, iron, aluminum, stainless, and steel, or can be formed of a resin. The shape of the floating core 5 may have a shape other than the spherical shape shown in
The pressure port 6 is connected to a pressurized fluid system (not shown) for pressure-injecting/discharging a pressurized fluid. The pressure port 6 is used for applying the pressurized fluid, supplied from the pressurized fluid system, to the back surface of the floating core 5 and pressing and moving the floating core 5 toward the other end 8 of the pipe portion cavity 1′. The pressurized fluid is pressure-injected through the pressure port 6 after the inside of the cavity 20 is filled with a resin. A resin gate 9 is provided at a position slightly apart from the floating core 5 so that in the injection of the molten resin through the resin gate 9, while the floating core 5 is pressed against the pressure port 6 without floating, the inside of the cavity 20 can be filled with the molten resin.
The pipe portion cavity 1′ has on the other end 8 side a communicating port 10, and an excess resin storage cavity 11 is communicated with the pipe portion cavity 1′ through the communicating port 10. Although the communicating port 10 has a size allowing the passage of the floating core 5, it is preferable that the communicating port 10 has a slightly constricted shape for ease of, for example, the cutting process to be performed later. When the pressurized fluid is pressure-injected through the pressure port 6 in such a state that the cavity 20 is filled with a resin, the floating core 5 is moved, whereby an excess resin is extruded from the pipe portion cavity 1′. The excess resin storage cavity 11 has a capacity capable of satisfactorily storing the excess resin and the floating core 5.
Although the means that opens and closes the communicating port 10 is not limited especially, there is means that opens and closes the communicating port 10 by moving a receiving shaft forward and backward by means of, for example, hydraulic pressure. Specifically, the receiving shaft passes through substantially the central portion of the excess resin storage cavity 10 to be retractably inserted toward the communicating port 10. When the receiving shaft advances, the peripheral edge of the front end is in press contact with the peripheral wall of the communicating port 10 to close the communicating port 10. The receiving shaft moves forward and backward, whereby the communicating port 10 is opened and closed. Alternatively, there can be adopted a method of opening and closing the communicating port 10 by means of, for example, hydraulic pressure, using a simply slidably opening and closing bar or the like.
Next, a specific procedure of injection molding using the mold shown in
As shown in
Then, as shown in
As the pressurized fluid, there is used a gas or liquid that does not react with or is not compatible with the resin to be used under injection molding temperature and pressure conditions. Specifically, nitrogen gas, carbon dioxide gas, air, glycerin, liquid paraffin, and so on can be used; however, an inert gas containing nitrogen gas is preferably used. In the pressure-injection of the pressurized fluid, when a gas such as nitrogen gas is used as the pressurized fluid, for instance, a pressurized gas as the pressurized fluid, whose pressure is raised by a compressor, is previously stored in an accumulator (not shown), and the pressurized gas is introduced into the pressure port 6 through a pipe, whereby the pressurized gas can be pressure-injected. Alternatively, the pressurized gas whose pressure is raised by a compressor is directly supplied to the pressure port 6, whereby the pressurized gas can be pressure-injected. Although the pressure of the pressurized gas supplied to the pressure port 6 is different depending on the kind of a resin to be used and the size of the floating core 5, it is usually approximately 4.90 to 29.42 MPa (50 to 300 kg/cm2G).
Subsequently, preferably, the resin is cooled while maintaining the inner pressure in the mold, and the pressurized fluid in the hollow 12 is discharged; thereafter, a molded product is removed. When a gas is used as the pressurized fluid, the pressurized fluid can be discharged by opening the pressure port 6 to the atmosphere. The pressurized fluid may be recovered into a recovery tank (not shown) for circulation utilization.
A secondary molded product (not shown) molded in the excess resin storage cavity 11 is separated from the removed molded product, whereby the resin molded body of this invention can be obtained. Although the secondary molded product can be easily separated by, for example, being cut near the communicating port, the communicating port 10 is previously formed into a constricted shape, whereby the secondary molded product can be more easily cut off to be separated.
The resin molded product of the following size shown in
Outer diameter: 7 mm
Inner diameter: 4.5 mm
100 mm×150 mm
As the floating core, a steel ball with a diameter of 4.5 mm is used, and a gas generator for gas hollow injection molding (“air mold” from Asahi Engineering Co., Ltd.) is used for the supply of a pressurized fluid. As the pressurized fluid, nitrogen gas is used. As a resin, a polyamide 66 resin (“LEONA 1300G” from Asahi Kasei Chemicals Corporation) containing 33% by weight of glass fiber is used.
First, as shown in
As shown in
When hot water of 60° C. is flowed from one side of the pipe portion of the obtained molded product to be discharged from the other side, the average temperature of the flat plate portion is 32° C., and the average temperature of the pipe portion is 54° C. Thus, the obtained molded product is suitable as a unit for heat-insulating. The temperature is measured at 8 points shown in
A molded product is obtained, using a PPS resin (“Torelina high thermal conducting material SH01 from Toray Industries, Inc.) as a resin, in a similar manner to the example 1, except that the resin temperature is 32° C.
When cooling water of 5° C. is flowed from one side of the pipe portion of the obtained molded product to be discharged from the other side, the average temperature of the flat plate portion is 18° C., and the molded product exhibits satisfactory performance as a unit for radiation.
The resin molded body of this invention is preferably used as, for example, a resin molded body for household equipment having a heat-insulating function, such as a wall and a floor heating, a resin molded body for automobile parts required to have a function of cooling and dissipating the heat of, for example, a cylinder head cover of a vehicle exposed to high temperature, and a resin molded body for home appliances and OA equipment required to have a function of cooling and dissipating the heat of a computer and so on.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-221058 | Aug 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/003737 | 8/5/2009 | WO | 00 | 5/13/2011 |
